1. Field of the Invention
The invention relates to integrated-circuit fabrication techniques and, more particularly, the invention relates to a method and apparatus for providing distributed material management and flow control in a fully automated integrated-circuit factory.
2. Description of the Background Art
An integrated circuit factory comprises a plurality of process tools that function together to form a process bay. The factory may contain a plurality of bays that operate to perform various steps to process a semiconductor wafer that, taken together, form a complete integrated circuit on the wafer. Each process bay contains a bay stocker for temporarily storing cassettes of wafers that will be processed by process tools within the bay. Additionally, a bay may include a xe2x80x9cmini-stockerxe2x80x9d that is used for temporarily storing cassettes that are awaiting transfer from tool-to-tool. A transport agent is used to move cassettes from stocker-to-tool, tool-to-tool, tool-to-mini-stocker, mini-stocker-to-tool, and tool-to-stocker. The transport agent may be one or more robots, a human, or any other device that transports cassettes of wafers from location to location. One example of a stocker is disclosed in U.S. Pat. No. 6,129,496, issued Oct. 10, 2000.
To efficiently produce integrated circuits the stockers, mini-stockers, and tools must be controlled such that the wafer cassettes move through the factory without bottlenecks, deadlocks, or idle tools. Therefore, there is a need in the art for a method and apparatus for providing distributed material management and flow control in fully automated integrated-circuit factories.
The present invention is a method and apparatus for providing distributed material management and flow control in an automated integrated-circuit (IC) factory. The IC factory comprises a factory stocker, a plurality of process bays and a factory transport agent for moving wafer cassettes between the bay and the stocker. Each of the bays comprises a bay stocker, a plurality of tools, a mini-stocker and a bay transport agent for moving wafers amongst the bay components. The invention uses partitioned bay stockers to facilitate deadlock avoidance or deadlock resolution. Additionally, various algorithms are used to detect wafer cassette movement situations where deadlocks may result from a wafer cassette movement within a bay and for resolving deadlocks when they occur. As such, the invention facilitates distributed flow control and distributed routing of wafer cassettes through a factory.